2.0 Analysis 2.1 Introduction 2.2 Technical Analysis 2.2.1 Introduction The initial description of the mechanical problem, as related by the Chieftain pilot to the Caravan pilot, was that the cylinder head temperature on one engine was high, followed some minutes later by a rough running engine. As the aircraft was manoeuvring in the Charlo area, witnesses described hearing an engine that was backfiring, and not running with the sound of consistent power. Communication from the pilot indicates that he was dealing with a significant loss of engine power on one engine. Both engines were subjected to rigorous examination to determine if there were any mechanical deficiencies or operating conditions that would account for such a loss of power. 2.2.2 Left Engine The left engine exhibited some potential for power loss. It showed signs of a lean fuel/air mixture and had badly worn spark plugs. However, several factors suggest that the left engine was operating normally. Misfiring spark plugs would lead to incomplete combustion causing low, rather than high, cylinder head temperatures. Excessively lean fuel/air mixture would result in a high cylinder head temperature, and could lead to detonation, pre-ignition and backfiring; however, there was no physical evidence that detonation or pre-ignition occurred. Damage to the left propeller suggests substantial engine power at impact. The spectral analysis showed a propeller speed that, when combined with the blade angle at impact, indicates an engine producing nearly full power. The exhaust stack analysis also supports a conclusion of normal power. 2.2.3 Right Engine